I. Field of the Invention
The present invention relates to communications systems employing message transmitting stations and relay stations to send messages to mobile vehicles. More specifically, the present invention relates to a novel and improved method and apparatus for utilizing such communications systems to enable remote monitoring and configuration of electronic control systems within commercial freight transportation vehicles.
II. Description of the Related Art
A need is recognized by many in the mobile vehicle environment for vehicle location and dispatch messaging capability. There are a substantial number of commercial, governmental, and private applications requiring the delivery of relatively short messages to or from a large number of geographically dispersed terminals, or mobile transceivers, often on an irregular basis. The need for message services includes, for example, aviation, navigation, commercial transportation, and message delivery services.
Other examples include the commercial trucking industry, where dispatchers wish to communicate short messages to trucks located anywhere in the continental United States, especially in rural areas. Until recently the transfer of such messages was restricted to periodic telephonic communication between drivers and a central dispatcher. However, it proved to be difficult, if not impossible, for drivers to consistently "call in" at fixed, scheduled, times since telephone services are not always readily available in many areas.
Aside from conventional telephone systems, other communication systems have attempted to address the mobile market. Radio telephone, cellular telephone, and portable radio transceivers (CB) are all capable of providing some form of communication between a mobile transceiver and a base unit. However, a number of factors have rendered these systems inadequate as message communication systems for serving a large number of widely dispersed users. For example, the lower power transmissions within each of an array of cells within cellular communication systems are prone to frequency selective fading and signal blocking. Moreover, highly mobile units such as trucks are required to frequently change channels as new cells within the cellular system are traversed. Direct communication, non-cellular radio systems have proven to be similarly disadvantageous due to frequent system overload and susceptibility to interference from other communications systems.
A communication system based on Earth orbital relay satellites has been developed in an effort to overcome these difficulties and provide for continuous delivery of messages and related control information to a large number of users over a wide geographic area. Such a satellite-based message communication system is described in, for example, U.S. Pat. No. 4,979,170, entitled ALTERNATING SEQUENTIAL HALF DUPLEX COMMUNICATION SYSTEM, which is assigned to the assignee of the present invention and which is herein incorporated by reference.
In addition to a dependence upon systems for providing messaging capability to remote mobile units, certain industries also share a requirement for reliable mobile unit location information. One industry in particular in which such information is particularly desirable is the commercial trucking industry. In the commercial trucking industry an efficient and accurate method of vehicle position determination is in demand. With ready access to vehicle location information, the trucking company home base obtains several advantages. The trucking company can keep the customer apprised of location, route and estimated payload time of arrival. The trucking company can also use vehicle location information together with empirical data on the effectiveness of routing, thereby determining the most economically efficient routing paths and procedures.
In U.S. Pat. No. 5,017,926, entitled DUAL SATELLITE NAVIGATION SYSTEM, which is assigned to the assignee of the present invention, there is disclosed a system in which the communications terminal at each mobile unit is capable of determining position in addition to providing messaging capability. The system of U.S. Pat. No. 5,017,926 relies upon the theory of trilateration in, for example, the determination of mobile vehicle position. Trilateration prescribes that if the position of three objects are known relative to each other, and the distance from each these three objects to a fourth object is known, then the three dimensional position of the fourth object can be determined within the coordinate frame which described the position of the first three objects. In the system of the U.S. Pat. No. 5,017,926, the first two of the three known positions correspond to the locations of a pair of satellites, while the third position is at the center of the Earth.
Using the satellite communication capability at each mobile terminal to provide vehicle position determination offers great advantages to the commercial trucking and related parcel delivery industries. For example, this capability obviates the need for truck drivers themselves, via telephones, to provide location reports regarding their vehicle position to the trucking company home base. These location reports are intermittent at best, because they occur only when the truck driver has reached a destination or stopover site, and require the expenditure of the driver's time to phone the trucking company home base. This method of location report also leaves room for substantial inaccuracies. For example, truck drivers may report incorrect location information either mistakenly or intentionally; or report inaccurate estimates of times of arrival and departure.
In contrast, the use of satellite communication capability at each truck enables the location trucking company home base to identify the longitude/latitude position of each truck at will, thus avoiding the disadvantages associated with intermittent location reports. For example, the down time (i.e., periods of zero revenue production) of idle trucks is minimized since the communications necessary for determining location could take place while trucks are en route. Also, inaccuracies in location reports are virtually eliminated because the trucking company home base is able to ascertain accurate truck location nearly instantaneously.
Recently, trucking and delivery vehicles have been equipped with electronic control units (ECUs) connected to a vehicle data link. Such on-board ECUs typically incorporate self-diagnostic features capable of, for example, detecting faulty engine operation and vehicle subsystem failure. Such ECU diagnostics tend to reduce maintenance costs by ensuring that each vehicle is serviced in a timely manner subsequent to detection of engine malfunction and the like. However, on-board vehicle electronic processing and memory resources have been found to lack the capacity to fully utilize the large amounts of data produced by increasingly sophisticated electronic vehicle control systems. The limited on-board processing capability of vehicle electronic control units have inhibited performance of sophisticated diagnostic procedures, and have similarly limited the execution of vehicle prognostics designed to anticipate vehicle servicing requirements.
In addition, many on-board ECUs are disposed to accumulate data relating to vehicle operation. Specifically, data is transmitted over the internal data link to an on-board recording device. However, the data accumulated by the on-board recording device is typically of utility only after it has been transferred to a home base computer for use in analysis of vehicle operation. The transfer of on-board data to the home base computer is usually accomplished by downloading the on-board data to a portable computer and physically transporting the computer to the home base. This has proven to be a cumbersome process which is also both costly and prone to error, especially within large vehicle fleets.
The operational parameters of many on-board vehicle ECUs may also be programmed so as to optimize vehicle operation. For example, the vehicle engine ECU may be set to prevent the vehicle from exceeding a maximum vehicle speed. Again, however, adjustment of ECU parameters is typically accomplished through manual connection of a specially programmed portable computer to the vehicle electronic system. This manual parameter adjustment process is similarly expensive and prone to error.
During both the accumulation of on-board operational data and the adjustment of ECU parameter settings, communication over the data link is performed by using protocols which are proprietary to the manufacturer of each ECU. The existence of multiple protocols adds cost and complexity to the system, and precludes standardized communication over the vehicle data link. Furthermore, existing proprietary protocols for communication over the vehicle data link generally do not provide for reliable verification of the identity of the devices currently connected to the link. That is, it is typically incumbent upon vehicle drivers or service personnel to manually maintain a record of various identifying information (e.g., manufacturer, model number, software version) associated with each ECU connected to the data link. Such manual verification methods are also obviously quite susceptible to human error.